Water-based flushing solutions are generally used for cleaning waterborne paints out of automated and manual spraying systems as well as from the external surface of the spraying equipment.
Conventional water-based flushing solutions comprise a component of amines and a component of organic solvent generally selected from the group consisting of simple alcohols and monoethers of glycols, most or all with molecules that contain no more than eight carbon atoms, in order to have sufficient water solubility. The amines used are typically alkanolamines like dimethyl ethanol amine, methyl isopropanol amine, and diethanol amine but are not limited to this class of amines. Typical solvents used in the solution are alcohols and glycol ethers, such as n-butanol, ethylene glycol mono butyl ether, diethylene glycol n-butyl ether, triethylene glycol methyl ether, propylene glycol normal butyl ether, dipropylene glycol methyl ether, propylene glycol methyl ether, and propylene glycol normal propyl ether. Typical concentrate formulas consist of 85 to 99% of solvent and 1 to 15% of alkanolamine, with the balance water. The concentrates are usually diluted to from 5% to 15%, by weight or volume, in deionized water for use as a working water-based paint-removing solution. Operating temperature when using the water-based solution is usually from 21 to 55° C.
Many of the constituents of the conventional water-based flushing solutions are legally classified as “volatile organic compounds”, hereinafter usually abbreviated as “VOC”. Although these high VOC content paint removing solutions are effective at removing paint, they have the drawback of high VOC emissions that are a source of both indoor and outdoor air pollution and can cause harmful health effects. Lower VOC content paint removing solution, however, have not been as effective at removing paints or other coatings. In particular, low VOC content paint removing solutions have not been effective at removing paints and coatings based on a urethane dispersion resin. Significantly, many of the newer waterborne paints are based on these urethane dispersion systems that are more difficult to solubilize using low VOC based cleaning formulations.
Accordingly, a need exists for flushing or cleaning solutions effective for cleaning paints, including paints based on a urethane dispersion resin, while maintaining low VOC content and/or emissions. A need also exists for flushing solutions that are effective at removing coatings at or near ambient temperatures. The present invention addresses the drawbacks of the prior art and meets the above-identified needs.